求助ansys做转子动力学遇到的问题

用ansys做 转子动力学时，遇到如下提示：At least one of the frequencies is unstable. Instability check is mode on real part of eigenvalue. If damping is very small,re-runing the model using another eigensolver is strongly .recommend to double-check the instability prediction
请问是何原因，如何解决呢？